1. Field of the Invention
The present invention is directed in general to integrated circuit devices and methods for manufacturing same. In one aspect, the present invention relates to the manufacture and use of semiconductor devices used for electrostatic discharge (ESD) protection in integrated and other circuits.
2. Description of the Related Art
To protect against electrostatic discharge (ESD) events in integrated circuit devices, ESD protection or clamp devices are typically provided as voltage limiting devices across the inputs and/or other terminals of such integrated circuit devices. ESD protection devices are intended to remain quiescent during normal operation of the associated integrated circuit devices when used with normal operating voltage Vo, but turn on when excessive voltage arises, thereby preventing damage to any protected elements in the integrated circuit devices. Some ESD clamp circuits use bipolar transistors and/or silicon controlled rectifier circuits (a.k.a., thyristor circuits) between the protected terminals which turn “on” at an initial triggering threshold voltage Vt1, and conduct current when voltage across the protected terminals rises beyond a predetermined triggering threshold voltage or limit. The initial trigger voltage Vt1 is usually closely correlated to DC BV for breakdown-triggered devices. In operation, as the voltage applied to the terminals is increased, very little current flows through the ESD clamp circuit until the triggering threshold voltage Vt1 is reached, at which point the ESD clamp circuit begins conducting current up to a snapback point (defined by a higher holding current Isb and lower holding voltage Vsb) after which, depending upon the internal on-state resistance RON of ESD claim circuit, the current and voltage may further increase to second trigger or breakdown point (Vt2, It2) beyond which destructive failure may occur leading to further current increase accompanied by voltage decrease.
Further limitations and disadvantages of conventional processes and technologies will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings and detailed description which follow.
It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for purposes of promoting and improving clarity and understanding. Further, where considered appropriate, reference numerals have been repeated among the drawings to represent corresponding or analogous elements.